1. Field of the Invention
The present invention relates to modelling for creating a configuration model in three-dimensional (hereinafter refferred to as 3D) computer graphics.
2. Description of the Related Art
3D computer graphics (3D-CG) are a technique for three-dimensionally displaying a real object or a virtual object on a screen on the basis of a three-dimensional configuration model of the object. By establishing a three-dimensional space inside a computer, it is possible to display scenery viewed from an optional point of view. Simulation/presentation games are a typical application of 3D-CG.
It is necessary to register models such as a configuration, a surface attribute and a motion in a computer to realize a three-dimensional display. A displaying quality depends on a model. While automatic modelling of a real object is under development, at present, automatic modelling is insufficient for a practical use. Modelling for creating a model of a complex configuration by combining a plurality of models through dialog between a computer and a human being (operator) is therefore desired.
A known modelling method uses real image photographing of a real object to create a three-dimensional configuration model of the object. A two-dimensional image including three-dimensional structure information, such as a perspective view, may be used instead of the real image. In a modelling system adopting this modelling method, an existing model and a real image are arranged in a virtual three-dimensional space (global coordinate space) to display on a screen a monitor image which shows a positional condition. Existing models are models having basic configurations (basic models) such as a cubic configuration, a circular cylindrical configuration, a conical configuration and a spherical configuration or object models of incomplete conditions (target object models). A monitor image is obtained by synthesizing a real image and a projection image of an existing model onto a plane which includes the real image. An operator operating the modelling system corrects the existing model so that the projection image of the existing model accords with an object in the real image. For example, an operator deforms the projection image by means of dragging of a mouse (in a similar manner to that for correcting a figure in a two-dimensional CAD). While operating, the operator can visually observe a model by instinct. This modelling method is superior to a method which requires to input an appearance size of an object on the basis of a design drawing or surveyed data, in terms of operation easiness.
Modification of a model in a monitor image is disclosed in Japanese Patent Application Laid-Open No. 6-348815 (1994). Japanese Patent Application Laid-Open No. 3-138784 (1991) describes to select a model which is similar to an object from a plurality of existing models and to use the same.
By the way, a method which requires to assort a plurality of models to create a model of a target object (hereinafter referred to as an object model) is widely used in computer graphics.
However, in the case where a real image is utilized for modelling, there is no example in which the method is applied. In other words, since an object model must be created by correcting only one existing model in a conventional technique, to make it possible to create a complex object model, it is necessary to prepare various types of existing models in advance.